Nicotine- and arecoline-induced interleukin-1 secretion and intercellular adhesion molecular-1 expression in human oral epidermoid carcinoma cells in vitro

Arecoline Induces ROS Accumulation, Transcription of Proinflammatory Factors, and Expression of KRT6 in Oral Epithelial Cells

Areca nut is a major contributor to the high prevalence of oral cancer in Asia. The precise mechanisms by which areca nut stimulates mucosal cells and contributes to the progression of oral cancer urgently require clarification. The current study aimed to assess the effects of arecoline on the normal human gingival epithelium cell line S-G. Cell viability, levels of reactive oxygen species (ROS), protein expression, cellular morphology, and gene expression were evaluated using the MTT test, flow cytometry, Western blot analysis, optical or confocal microscopy, and RT-qPCR. Keratin (KRT6) analysis involved matched normal and cancer tissues from clinical head and neck specimens. The results demonstrated that 12.5 µg/mL of arecoline induced ROS production, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) mRNA expression in S-G cells. This activation of the MAPK/ERK pathway increased KRT6 expression while limiting cell migration. In head and neck cancer tissues, KRT6B gene expression exceeded that of normal tissues. This study confirms that arecoline induces ROS accumulation in normal cells, leading to the secretion of proinflammatory factors and KRT6 expression. This impedes oral mucosal healing, thereby promoting the progression of oral cancer.

Nicotine Inhibits Cisplatin-Induced Apoptosis via Regulating α5-nAChR/AKT Signaling in Human Gastric Cancer Cells

Gastric cancer incidence demonstrates a strong etiologic association with smoking. Nicotine, the major component in tobacco, is a survival agonist that inhibits apoptosis induced by certain chemotherapeutic agents, but the precise mechanisms involved remain largely unknown. Recently studies have indicated that α5-nicotinic acetylcholine receptor (α5-nAChR) is highly associated with lung cancer risk and nicotine dependence. Nevertheless, no information has been available about whether nicotine also affects proliferation of human gastric cancer cells through regulation of α5-nAChR. To evaluate the hypothesis that α5-nAChR may play a role in gastric cancer, we investigated its expression in gastric cancer tissues and cell lines. The expression of α5-nAChR increased in gastric cancer tissue compared with para-carcinoma tissues. In view of the results, we proceeded to investigate whether nicotine inhibits cisplatin-induced apoptosis via regulating α5-nAChR in gastric cancer cell. The results showed that nicotine significantly promoted cell proliferation in a dose and time-dependent manner through α5-nAChR activation in human gastric cells. Furthermore, nicotine inhibited apoptosis induced by cisplatin. Silence of α5-nAChR ablated the protective effects of nicotine. However, when co-administrating LY294002, an inhibitor of PI3K/AKT pathway, an increased apoptosis was observed. This effect correlated with the induction of Bcl-2, Bax, Survivin and Caspase-3 by nicotine in gastric cell lines. These results suggest that exposure to nicotine might negatively impact the apoptotic potential of chemotherapeutic drugs and that α5-nAChR/AKT signaling plays a key role in the anti-apoptotic activity of nicotine induced by cisplatin.

Interleukin-1 and interleukin-8 in nicotine- and lipopolysaccharide-exposed gingival keratinocyte cultures

BACKGROUND AND OBJECTIVE

Tobacco use is associated with increased periodontal destruction in both cigarette smokers and smokeless tobacco users. Gingival keratinocytes are the first cells in contact with microbial and tobacco components and play a key role in the innate immune response to these agents. The objective of this study was to evaluate the effect of nicotine and bacterial lipopolysaccharide (LPS) alone and in combination on gingival keratinocyte production of interleukin-1 alpha (IL-1 alpha) and interleukin-8 (IL-8).

MATERIAL AND METHODS

Gingival keratinocyte cultures were established from 10 healthy, non-tobacco-using subjects. The cells were stimulated for 24 h with 1 mum or 1 mm nicotine and/or 10 microg/mL Escherichia coli or Porphyromonas gingivalis LPS. Interleukin-1 alpha and IL-8 proteins were quantified using ELISAs.

RESULTS

Compared with untreated cultures, 1 mm nicotine stimulated production of IL-1 alpha (p < 0.001); E. coli and P. gingivalis LPS increased IL-8 production (p = 0.0014 and p = 0.0232, respectively). A combination of nicotine and LPS produced the highest cytokine quantities. Amounts of IL-1 alpha and IL-8 following 1 mm nicotine and LPS exposure were significantly greater than in untreated cultures (p < 0.001). Interleukin-8 was also responsive to 0.1 mum nicotine combined with E. coli or P. gingivalis LPS compared with control cultures (p < 0.0001 and p = 0.0029, respectively). Both cytokines tended to be elevated following the combined treatment relative to nicotine or LPS treatment alone.

CONCLUSION

These results demonstrate that nicotine and LPS differentially regulate IL-1 and IL-8 production by gingival keratinocytes. Combined treatment tended to elevate cytokine production further, which may have implications for the progression of periodontitis in tobacco users.

Nicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone induce cyclooxygenase-2 activity in human gastric cancer cells: Involvement of nicotinic acetylcholine receptor (nAChR) and beta-adrenergic receptor signaling pathways

Induction of cyclooxygenase-2 (COX-2) associates with cigarette smoke exposure in many malignancies. Nicotine and its derivative, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are the two important components in cigarette smoke that contributes to cancer development. However, the molecular mechanism(s) by which nicotine or NNK promotes gastric carcinogenesis remains largely unknown. We found that nicotine and NNK significantly enhanced cell proliferation in AGS cells that expressed both alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) and beta-adrenergic receptors. Treatment of cells with alpha-bungarotoxin (alpha-BTX, alpha7nAChR antagonist) or propranolol (beta-adrenergic receptor antagonist) blocked NNK-induced COX-2/PGE(2) and cell proliferation, while nicotine-mediated cell growth and COX-2/PGE(2) induction can only be suppressed by propranolol, but not alpha-BTX. Moreover, in contrast to the dependence of growth promoting effect of nicotine on Erk activation, inhibitor of p38 mitogen-activated protein kinase (MAPK) repressed NNK-induced COX-2 upregulation and resulted in suppression of cell growth. In addition, nicotine and NNK mediated COX-2 induction via different receptors to modulate several G1/S transition regulatory proteins and promote gastric cancer cell growth. Selective COX-2 inhibitor (SC-236) caused G1 arrest and abrogated nicotine/NNK-induced cell proliferation. Aberrant expression of cyclin D1 and other G1 regulatory proteins are reversed by blockade of COX-2. These results pointed to the importance of adrenergic and nicotinic receptors in gastric tumor growth through MAPK/COX-2 activation, which may perhaps provide a chemoprevention strategy for cigarette smoke-related gastric carcinogenesis.

Nicotine induces the fragile histidine triad methylation in human esophageal squamous epithelial cells

The fragile histidine triad (FHIT) gene has been proposed to have an important role in very early carcinogenesis. Methylation of the FHIT gene is associated with transcriptional inactivation in esophageal squamous cell carcinoma, and FHIT inactivation has been linked to smoking-related carcinogenesis. In this study, we confirmed methylation of the FHIT gene in human esophageal squamous epithelial cells (HEECs) and examined whether nicotine induced alteration of FHIT. Methylation status in the promoter region of the FHIT gene and p16(INK4A) gene was determined by methylation-specific PCR in HEECs exposed to nicotine under various conditions. Methylation status of the FHIT gene was confirmed by DNA-sequencing analysis. Protein expression of Fhit and the DNA methyltransferases (DNMTs) DNMT1 and DNMT3a were assessed by immunoblot analysis. In the absence of nicotine, methylation of the FHIT gene and attenuation of Fhit protein were not detected in HEECs. Nicotine induced the methylation of FHIT gene and attenuated Fhit protein in association with increased expression of DNMT3a. Reexpression of Fhit protein in HEECs was found after cessation of moderate- to long-term exposure to nicotine. Our results show that nicotine induces methylation of the FHIT gene followed by loss of Fhit protein expression in HEECs. Continuous smoking may thus increase the risk of esophageal cancer.

Interleukin-4 gene, but not the interleukin-1 beta gene polymorphism, is associated with oral cancer

We aimed to evaluate whether polymorphisms of the interleukin-4 (IL-4) gene promoter and intron 3 regions, and polymorphisms of the IL-1 beta gene promoter and exon 5 regions are associated with oral cancer. This study included 130 patients with oral cancer and 105 age-matched healthy controls who lived in the same area as the patients. Each genetic polymorphism was typed by polymerase chain reaction (PCR)-based restriction analysis. We then compared the genotype distribution and allelic frequencies of each polymorphism between the oral cancer patients and the controls. The CC homozygote genotype of the IL-4 gene promoter -590 region differed significantly between the patients with oral cancer and the controls (odds ratio (OR)=6.0, 95% confidence interval (CI)=1.2-30.7, chi-square test, P=0.044). No significant difference in either the genotype distribution or the allelic frequencies of the IL-1 beta gene polymorphisms was observed between patients with oral cancer and controls. The IL-4 gene -590 C/T polymorphism is associated with oral cancer and is a suitable genetic marker for screening for oral cancer. However, whether the -590 C/T polymorphism of the IL4 gene plays a role in oral cancer remains unclear. Further substantiation based on larger patient samples is needed.

Exposure to Nicotine during Gestation Interferes with the Colonization of Fetal Bone Marrow by Hematopoietic Stem/Progenitor Cells

Environmental factors, including cigarette smoke components, can cross the placental barrier and accumulate in amniotic fluid and fetal tissue, and, therefore, interfere with the normal course of ontogenesis. Although cigarette smoke contains numerous compounds, the most adverse effects on mammalian tissues have been associated with nicotine. The aim of this study was to investigate the effect of intrauterine exposure to nicotine on hematopoiesis during fetal development and postpartum. Intrauterine exposure of mice to nicotine resulted in a more than two-fold reduction of the delayed- type hypersensitivity (DTH) response and a 2.5-fold decrease in the number of plaque forming cell (PFC) in offspring after 1 month of postnatal life, and correlated with low counts of mature lymphocytes and lymphoid progenitors in hematopoietic tissues. Neonates exposed to nicotine during gestation showed a significant decrease in the number of bone marrow hematopoietic progenitors, as measured by colony-forming unit (CFU) and long-term culture initiating cell (LTC-IC) assays, and decreased concentration of interleukin-6 (IL-6) in their serum. Analysis of the fetal bone marrow (E15) obtained from nicotine-exposed fetuses demonstrated a lower number of hematopoietic progenitors, whereas their number in the fetal liver was not significantly changed. Our data provide evidence that by targeting the nicotinic acetylcholine receptor (nAChR) nicotine interferes with the fetal development of the hematopoietic system. Inferior colonization of the fetal bone marrow by hematopoietic stem/progenitor cells (HSPC) subsequently results in an imbalance of mature blood and immune cell production after birth.